1. Field of the Invention
The present invention relates to a method of and an apparatus for evaluating a function for diagnosing a transient response of a variable valve mechanism adapted for changing operating characteristics of an engine valve.
2. Description of the Related Art
Japanese Unexamined Patent Publication No. 2000-073794 discloses a technique in which a deviation between a desired value and an actual value of the operating characteristics of the engine valve is calculated, and when a state where the deviation exceeds a determination value continues for a time period equal to or more than a predetermined time period, an occurrence of response delay in the variable valve mechanism is diagnosed.
If the diagnosing processing normally functions, it is possible to warn or alert a driver about such an abnormal condition that the response delay is increased. However, if the diagnosing processing does not function normally, the engine must be operated under a condition that a large response delay occurs and thus, performance at the time of acceleration of the engine accompanying changeover of desired operating characteristics of the engine valve is deteriorated.